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Kosuge, Atsushi; Ando, Kota*; Yamamoto, Keisuke*; Nakajima, Takashi*
Optics & Laser Technology, 201, p.115269_1 - 115269_6, 2026/09
Times Cited Count：0 Percentile：0.00(Optics)Nakase, Masahiko*; Nakazawa, Ryota*; Mishima, Ria
Next Chemical Engineering (Internet), 2, p.100051_1 - 100051_14, 2026/06
Tameta, Yuito; Sano, Kyohei; Takano, Yugo*; Yamamoto, Masahiko; Nakazaki, Katsutoshi; Akiyama, Kazuki
JAEA-Technology 2026-004, 27 Pages, 2026/05
JAEA-Technology-2026-004.pdf:3.18MB
At the High Active Solid Waste Storage (HASWS) of Tokai Reprocessing Plant, high active solid waste generated from the reprocessing process is stored. In the wet cell, hull cans containing fuel cladding tubes (hulls) and end pieces are stored, along with used filters and contaminated equipment. It is being considered that utilizes a small underwater remotely operated vehicle (ROV) along with a lifter for recovering and transporting objects from the seafloor for the retrieval of the waste stored in the HASWS. Mock-up tests were conducted in FY2022 and FY2023 to verify the feasibility of retrieving waste using the ROV and the lifter. In this study, to achieve safer and more reliable waste retrieval, improvements were made to each component, including the ROV cable, waste gripping grab, lifting hook, lifter, and ROV monitoring camera, and data were collected to evaluate operational performance. For the ROV cable, attaching a float to the rear section of the ROV cable to reduce its weight facilitated forward-tilt operation and improved the ROV's attitude stability during wire-cutting. For the waste gripping grab, attaching a jig to the tips of the grab of the lifter (grabtype) enhanced the gripping stability of the hull can. For the lifting hook, setting the ring diameter of the lifter (hook-type) to 15 cm shortened the time required for grasping and improved accessibility to the hook. For the lifter, using lifters with modified internal structures enabled fine air-volume adjustment and reduced blockage of air passages, thereby improving the stability of air supply and exhaust. For the ROV monitoring camera, adding a light near the ROV monitoring camera in a dark environment ensured sufficient cell illumination and enhanced cable visibility.
Department of Decommissioning and Waste Management
JAEA-Review 2026-008, 39 Pages, 2026/05
JAEA-Review-2026-008.pdf:1.7MB
This report summarizes the activities carried out in FY2024 by the Department of Decommissioning and Waste Management (DDWM) at the Nuclear Science Research Institute (NSRI). It provides an overview of the operations and maintenance of the assigned facilities, the treatment and management of radioactive waste, decommissioning activities, and related technical development work. In FY2024, radioactive waste generated from R&D activities at NSRI was safely treated, including approximately 165 m
of combustible solid waste, 185 m of non-combustible solid waste, and 232 m of liquid waste. As of the end of FY2024, the cumulative volume of stored waste packages reached 119,601 (in 200-liter drum equivalents), representing an increase of 937 packages compared with the previous fiscal year. In addition, efforts were made to comply with the new regulatory requirements for waste management facilities. With regards to decommissioning activities, equipment removal and related work were carried out at the Japan Reprocessing Test Facility (JRTF) and the Plutonium Research Building No.1. In the field of technical development, radioactivity data were obtained from waste samples toward the establishment of waste radioactivity evaluation methods. Furthermore, at the request of the Ministry of the Environment and Tokai-mura office, JAEA conducted a demonstration project on the landfill disposal of the contaminated soil generated by the accident of the Fukushima Daiichi Nuclear Power Station.
Takubo, Yusaku*; Takayama, Yusuke*; Sugita, Yutaka; Ogoshi, Minori; Ishida, Keisuke*
Environmental Earth Sciences, 85(9), p.229_1 - 229_19, 2026/05
Times Cited Count：0Hayano, Akira
Nihon Genshiryoku Gakkai-Shi ATOMO
, 68(5), p.311 - 315, 2026/05
no abstracts in English
Noseck, U.*; Sch
fer, T.*; Alonso, U.*; Hamamoto, Takafumi*; Havlova, V.*; Hibberd, R.*; Ishidera, Takamitsu; Kitamura, Akira; Klajmon, M.*; Missana, T.*; et al.
Applied Geochemistry, 201, p.106762_1 - 106762_23, 2026/04
Times Cited Count：0 Percentile：0.00(Geochemistry & Geophysics)Thermodynamic benchmark calculations have been performed to better understand the behavior of 
Se(VI), 
Tc(VII), 
U(VI), 
Np(V), 
Am(III), Th(IV) and 
Pu(IV)) in the evolving geochemical conditions of the Long-term In-situ Test (LIT) at the Grimsel Test Site (GTS) and corresponding mock-up experiment. It also aims to identify the status of the geochemical speciation models and databases for these elements. The experiments are simulating the near-field conditions in some radioactive waste repository concept including a bentonite engineered barrier emplaced in crystalline rock and the findings are contributing to the long-term safety assessment of these facilities.
Kondo, Masatoshi*; Kitamura, Yoshiki*; Kawarai, Atsushi*; Saito, Shigeru; Obayashi, Hironari
Corrosion Science, 262, p.113646_1 - 113646_14, 2026/04
Times Cited Count：0 Percentile：0.00(Materials Science, Multidisciplinary)The corrosion resistance of FeCrAl alloy APMT (Fe-21Cr-5Al-3Mo) in flowing lead-bismuth eutectic (LBE) was investigated by corrosion tests performed at 723 K using a non-isothermal forced convection loop. The oxygen concentration in flowing LBE was controlled at 1
10
wt%. No severe corrosion or erosion was detected on the specimens exposed to flowing LBE for 2000 h and 4000 h. Multiple oxide layers consisting of Fe-rich, Cr-rich and Al-rich sub-layers were formed in situ on the surface of APMT during the corrosion tests, which effectively suppressed corrosion and erosion. The oxide layers were intentionally removed by gentle abrasion prior to re-immersion and the specimens were then re-immersed in flowing LBE for an additional 2000 h. The oxide layers were spontaneously re-formed in situ on the abraded surface. This behavior indicates a self-healing capability. The results of micro-scratch tests indicated that the in-situ formed multiple oxide layers exhibited high adhesion strength in the shear direction after the 2000 h corrosion test.
Nagata, Shohei*; Aoyagi, Kazuhei; Fujieda, Daigo
Mitigation of Major Safety Risks Specific to Long and Deep Tunnel Construction; ITA Working Group 17; Long Tunnels at Great Depth; ITA Report No.42 (Internet), p.137 - 141, 2026/04
no abstracts in English
Ozaki, Yusuke
Nihon Genshiryoku Gakkai-Shi ATOMO, 68(4), p.224 - 228, 2026/04
The Japan Atomic Energy Agency launched the Horonobe International Project (HIP) utilizing the Horonobe Underground Research Laboratory. Of the three tasks established for the HIP, Task A focuses solute transport experiment with model testing. The scope of task A includes field experiments, laboratory experiments, and numerical modeling. This article provides an overview of the activities, results, and status of international collaboration during phase 1.
Tani, Riku; Inoue, Satoshi*; Mizoguchi, Takafumi*; Suda, Shoya; Nakajima, Ryota; Inoue, Hidetaka*; Kurabeishi, Nariaki*; Ouchi, Yasuhiro; Haraga, Tomoko; Shimizu, Osamu
JAEA-Technology 2025-018, 32 Pages, 2026/03
JAEA-Technology-2025-018.pdf:2.4MB
With rising summer temperatures, the number of heatstroke incidents at worksites has been increasing. Even short-term exposure to high-temperature and high-humidity environments can result in serious health hazards. In recent years, measures to prevent heatstroke in the workplace have been legally mandated, requiring employers to manage the work environment and ensure workers' health. At the JAERI Reprocessing Test Facility (JRTF), basic heatstroke prevention measures such as pre-shift health checks and strategic placement of water stations have been implemented. However, due to rising workplace temperatures and longer work durations, these conventional measures alone were considered insufficient to adequately reduce risk. This year, large spot coolers were installed, and cooling vests were introduced to improve both the work environment and individual thermal load. Data on temperature, humidity, and WBGT values were collected before and after the implementation to evaluate the effects on environmental conditions and worker comfort. This report aims to assess the effectiveness of specific countermeasures in reducing the risk of heatstroke during decommissioning work and to inform future improvements to the work environment.
Yoshinaka, Kazuyuki
JAEA-Review 2025-063, 50 Pages, 2026/03
JAEA-Review-2025-063.pdf:3.84MB
In the decommissioning of reprocessing facilities, one of the reasons why a safe storage period is usually not set is that Pu-241 decays into Am-241, which accumulates in the process. As eighteen years have passed since the Tokai Reprocessing Plant finished its operation in 2007, it was considered during recent work that the relative proportion of Am-241 has increased compared to earlier measurements. Therefore, this trend was investigated using records of 
nuclide analyses conducted during operations. In this investigation, we focused on and discussed the relative proportion of the major nuclide, Cs-137 and Am-241. The survey confirmed that the proportion of Am-241 tended to increase in all process equipment, though the extent of the increase varied depending on the process. In operations related to spent fuel storage systems, decontaminating when moving fuel, and the solubility of Cs-137 have an effect. In recent years, there have even been cases where Am-241 accounted for 80 % to 90 % of the nuclides detected. In operations related to mechanical processes, including the shearing equipment, the increase appears to correspond to the composition of the spent fuel, and the proportion of Am-241 in all nuclides can exceed 40 % in some cases. In operations related to vitrification process, while the increase seems to correspond to the composition of the high-level radioactive waste, the proportion of Am-241 among all nuclides has not exceeded 10 % in any case. In operations related to radioactive liquid waste processes, the precipitate components at the bottom of storage tanks have an effect and Am-241 tends to be detected at a high proportion. In operations related to incineration processing of radioactive solid waste, the overall trend is thought to correspond to the type of waste handled, but relatively high proportions of Am-241 have been detected on internal walls of incinerators and similar areas.
Nonoue, Kazuki; Koda, Yuya
JAEA-Review 2025-060, 19 Pages, 2026/03
JAEA-Review-2025-060.pdf:3.22MB
"Fugen Decommissioning Engineering Center", in planning and carrying out our decommissioning technical development, organizes "Technical special committee on Fugen decommissioning" which consists of the members well-informed, aiming to make good use of Fugen as a place for technological development which is opened domestic and international, as the central place in research and development base of Fukui prefecture, and to utilize the outcome in our decommissioning to the technical development effectively. This report consists of presentation papers "The current status of Fugen decommissioning" and "Considerations of dismantling of the reactor core (including basic design report)" which are presented in the 42nd Technical Special Committee on Fugen Decommissioning.
Ningyo-toge Environmental Engineering Center
JAEA-Review 2025-059, 51 Pages, 2026/03
JAEA-Review-2025-059.pdf:6.2MB
This report outlines some main research and development activities executed by the Ningyo-toge Environmental Engineering Center in FY2024. The Center was working on the development of the nuclear fuel cycle with a focus on its frontend (i.e., uranium exploration, mining, refining, conversion, and enrichment) until 2001, and is now dismantling and removing the facilities and equipment used in the past. In addition, based on the concept of "Uranium and environmental research platform" announced in 2016, we are also working on research and development for the safe processing and disposal of uranium wastes. This research and development can be mainly divided into "Environmental research" and "Uranium waste engineering research"; the former takes advantage of the characteristics of the natural environment in Ningyo-toge, and the latter utilizes our facilities and potentials. Some works are also made on safety and its management as well as radiation effect research in terms of health physics and radiobiology. Regarding the environmental research and environmental conservation, this report describes research on the heterogeneity of groundwater in granitic mountains and the mineral immobilization of long-lived anionic nuclides. As for the uranium waste engineering research, the laser-based decontamination technique and the corrosion resistance suitable for waste package material are reported. Further, the construction of safety measures at the mill tailings ponds, the data analysis of safety information, and the environmental fate of radon are also reported. The achievements of those works have been widely presented through research papers etc.
Hoshino, Masato; Sasaki, Yoshifumi; Horikoshi, Hidehiko*; Tani, Kosuke*
JAEA-Review 2025-047, 122 Pages, 2026/03
JAEA-Review-2025-047.pdf:3.75MB
Horonobe Underground Research Center managed by Japan Atomic Energy Agency (JAEA) is the Japan's best environment to understand the project of geological disposal of high-level radioactive waste, because there is an Underground Research Laboratory (URL) in the center besides an exhibition facility which explains the content of research conducted in the URL. In the area of the center, there is also an exhibition facility for the full-scale model of engineered barrier system of geological disposal. JAEA takes advantage of this opportunity to conduct public hearing including questionnaire research regarding the questions, anxieties and comments by the visitors for geological disposal project. This report summarizes the result of statistical analysis of 2,830 visitors from April 2024 to January 2025.
Nakayama, Masashi; Ishii, Eiichi; Aoyagi, Kazuhei; Hayano, Akira; Ono, Hirokazu; Ozaki, Yusuke; Mochizuki, Akihito; Takeda, Masaki; Kimura, Shun
JAEA-Research 2025-016, 141 Pages, 2026/03
JAEA-Research-2025-016.pdf:13.37MB
The Horonobe Underground Research Laboratory (URL) Project is being pursued by the Japan Atomic Energy Agency (JAEA). The main aim of the project is to enhance the reliability of relevant technologies for the geological disposal of high-level radioactive waste by investigating the deep geological environment within the host sedimentary rocks at Horonobe in Hokkaido, northern Japan. These investigations have been conducted in three phases: "Phase 1: Surface-based investigation", "Phase 2: Construction" (investigation during tunnel excavation) and "Phase 3: Operation" (investigation in subsurface facilities). Since the fiscal year 2020, we have been conducting R&D based on the Horonobe Underground Research Plan for the Fiscal Year 2020 Onwards, which was approved by Hokkaido Prefecture and Horonobe Town. In particular, we are working on the following key tasks with the aim of completing JAEA's 3rd and 4th Mid- and Long-Term Plans: "Study on near-field system performance in geological environments", "Demonstration of repository design options" and "Understanding of buffering behaviour of sedimentary rocks to natural perturbations". This report summarizes the R&D activities on the three above-mentioned key tasks, the goals of which were achieved between fiscal years 2020 and 2024. The results obtained from these tasks will be systematically organized as part of the "Systematic integration of technologies towards EBS emplacement" which has been in progress since fiscal year 2024. This task includes concepts related to the layout of galleries and pits, installation methods for engineered barrier materials, and methods for evaluating their containment performance.
Matsubara, Akihiro*; Uno, Sadanori*; Miyake, Masayasu*; Maeta, Yusuke; Omae, Akiomi*; Kitano, Toshihiko*; Fujita, Natsuko
Dai-37-Kai Tandemu Kasokuki Oyobi Sono Shuhen Gijutsu No Kenkyukai Hokokushu, p.114 - 117, 2026/03
no abstracts in English
Fujita, Natsuko; Maeta, Yusuke; Miyake, Masayasu*; Matsubara, Akihiro*; Uno, Sadanori*; Omae, Akiomi*; Jinno, Satoshi; Minamitani, Fumina; Watanabe, Takahiro; Nishio, Tomohiro; et al.
Dai-37-Kai Tandemu Kasokuki Oyobi Sono Shuhen Gijutsu No Kenkyukai Hokokushu, p.22 - 25, 2026/03
no abstracts in English
Mochizuki, Akihito; Yoshida, Hidekazu*
Enerugi Rebyu, 46(4), p.42 - 44, 2026/03
no abstracts in English
Hagiwara, Hiroki; Takaku, Atsushi*; Sagawa, Hiroshi*; Kanno, Futoshi*; Ito, Azusa; Ando, Taichi*; Ichihara, Masatsugu*; Watanabe, Yusuke; Koarai, Kazuma; Kato, Jun; et al.
Proceedings of Waste Management Symposia 2026 (WM2026) (Internet), 7 Pages, 2026/03
